Hard disk drives are an efficient and cost effective solution for data storage. Depending upon the requirements of the particular application, a disk drive may include anywhere from one to twelve hard disks and data may be stored on one or both surfaces of each disk. While hard disk drives are traditionally thought of as a component of a personal computer or as a network server, usage has expanded to include other storage applications such as set top boxes for recording and time shifting of television programs, personal digital assistants, cameras, music players and other consumer electronic devices, each having differing information storage capacity requirements.
As aerial bit densities of hard disks have dramatically increased in recent years, the large data storage capacities of dual-sided magnetic storage media far exceed demand in many applications. For example, dual-sided hard disks in personal computers have much greater storage capacity than most consumers require during the useful life of the computer. Consumers thus are forced to pay substantial amounts for excess data storage capacity. The intense price competition in the magnetic storage media industry has forced many disk drive manufacturers to offer single-sided magnetic storage media as an alternative. Single-sided storage media are of two types. In one type, a double-sided disk configured to store information on both sides of the disk is installed with a single read/write head serving only one side of the disk. In the other type, known as a single-sided processed disk, only one side of the disk is provided with an information-containing magnetic layer. The other side of the disk does not have an information-containing layer. Single-sided processed storage media not only have sufficient storage capacities to satisfy most consumers but also can be manufactured less expensively.
One frequently encountered problem in single-sided processed disk manufacture is distinguishing the media storage or active side of the disk from the inactive side of the disk. Distinguishing the two sides from one another can be extremely important not only in disk manufacture but also in disk installation during manufacture and later repair of the host device. If the active side position is reversed with the inactive side position during disk manufacturing, not only would the final disk have to be discarded leading to an enormous yield losses but also would the service life of processing equipment/components be substantially reduced. If the disk is installed upside down in an information storage device, the read/write head will be unable to effect information storage and retrieval. Moreover, the read/write head may be damaged during use due to the improper finish of the inactive side. The inactive side generally lacks proper thin film and lubrication layers.
As can be seen in FIG. 1, which is a cross-section of an outer periphery of a conventional magnetic disk, the inactive side 100 is indistinguishable from the active side 104. For example, an identical chamfer 108 is used on both sides of the disk 112; in other words, each chamfer has the same angle θ1, the same chamfer length l1, and the same length l1 of the chamfer surface 116. As will be appreciated, the chamfer is used for a variety of reasons, including controlling the chipping and distortion of the disk and also minimizing cassette material wear and abrasion during handling and shipment and to facilitate lead in of the read/write head on the disk during read/write operations.